U.S. patent application number 11/290491 was filed with the patent office on 2006-06-08 for ink jet recording head.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. Invention is credited to Ken Tsuchii.
Application Number | 20060119663 11/290491 |
Document ID | / |
Family ID | 36573686 |
Filed Date | 2006-06-08 |
United States Patent
Application |
20060119663 |
Kind Code |
A1 |
Tsuchii; Ken |
June 8, 2006 |
Ink jet recording head
Abstract
The present invention aims at providing an ink jet recording
head which controls an impulse force generated at the time of
disappearing of a bubble with keeping an energy efficiency of ink
ejection high. The ink jet recording head has a discharge port from
which ink is discharged, a pressure chamber by which energy for
ejection is given to ink, and a nozzle portion which makes the
pressure chamber and the discharge port communicate. The nozzle
portion includes a major diameter portion with a sectional area
larger than an area of the discharge port, and a minor diameter
portion, whose sectional area is smaller than that of the major
diameter portion, along an ink ejection direction, and the minor
diameter portion is provided between the major diameter portion and
pressure chamber.
Inventors: |
Tsuchii; Ken; (Sagamihara,
JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Assignee: |
CANON KABUSHIKI KAISHA
Tokyo
JP
|
Family ID: |
36573686 |
Appl. No.: |
11/290491 |
Filed: |
December 1, 2005 |
Current U.S.
Class: |
347/47 |
Current CPC
Class: |
B41J 2/1639 20130101;
B41J 2/1603 20130101; B41J 2002/14475 20130101; B41J 2/1404
20130101; B41J 2/1433 20130101 |
Class at
Publication: |
347/047 |
International
Class: |
B41J 2/16 20060101
B41J002/16 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 7, 2004 |
JP |
2004-354072 |
Claims
1. An ink jet recording head, comprising: a discharge port from
which ink is discharged; a pressure chamber by which energy for
ejection is given to ink; and a nozzle portion which makes the
pressure chamber and the discharge port communicate, wherein the
nozzle portion includes a major diameter portion with a sectional
area larger than an area of the discharge port, and a minor
diameter portion, whose sectional area is smaller than that of the
major diameter portion, along an ink ejection direction, and the
minor diameter portion is provided in a position nearer to the
pressure chamber than the major diameter portion.
2. The ink jet recording head according to claim 1, wherein a taper
portion which tapers off gradually toward the discharge port is
provided between the discharge port and the major diameter
portion.
3. The ink jet recording head according to claim 1, wherein a
sectional area of the minor diameter portion becomes small toward
the pressure chamber.
4. The ink jet recording head according to claim 1, wherein an
electrothermal transducing element which heats ink inside the
pressure chamber to generate a bubble in the ink is provided inside
the pressure chamber, and the ink is discharged from the discharge
port by pressure at the time of the generating of a bubble.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an ink jet recording head
which ejects ink to a recorded medium to record an image.
[0003] 2. Related Background Art
[0004] An example of a conventional ink jet recording head
(hereafter, this may be abbreviated a "recording head") is shown in
FIGS. 7A, 7B, 8A and 8B. FIGS. 7A, 7B, 8A and 8B are enlarged
sectional views near a discharge port 105 where ink is discharged.
Below the discharge port 105, a pressure chamber 103 in which a
heater 102 is provided, a nozzle portion 101 which makes the
pressure chamber 103 and discharge port 105 communicate, an ink
flow path 106 for supplying ink to the pressure chamber 103 are
provided. Ink supplied to the pressure chamber 103 through the ink
flow path 106 is heated by heat generated by the heater 102, and is
discharged by the pressure of a bubble, which is generated in the
ink at that time, from the discharge port 105 through the nozzle
portion 101.
[0005] The nozzle portion 101 of the recording head shown in FIGS.
7A and 7B has a constant area of a section which is orthogonal to
an ink ejection direction. On the other hand, in the nozzle portion
101 of the recording head shown in FIGS. 8A and 8B, an area of this
section becomes large as it is close to the pressure chamber 103.
Hereafter, the nozzle portion 101 shown in FIGS. 7A and 7B may be
called a "straight nozzle" and the nozzle portion 101 shown in
FIGS. 8A and 8B may be called a "tapered nozzle" for
distinguishment. Here, the ink flow resistance of a straight nozzle
is large, and hence, its energy efficiency of ink ejection is low.
Therefore, in order to raise the energy efficiency of ink ejection,
a tapered nozzle with small flow resistance becomes mainstream.
[0006] For example, when a distance OH from the discharge port 105
to a top face of the heater 102 is 75 .mu.m and the height H of the
ink flow path is 20 .mu.m, the thickness (length) of the nozzle
portion 1 of both of the straight nozzle and tapered nozzle become
55 .mu.m. In this case, the inertance and viscous resistance of
each nozzle portion 101 become as shown in Table 1. TABLE-US-00001
TABLE 1 Straight Tapered nozzle nozzle Taper 5.degree. Taper
12.degree. Taper 19.degree. Nozzle Inertance 1.12E-01 8.04E-02
5.72E-02 4.37E-02 portion Inertance 100 72 51 39 ratio (%) Viscous
2.28E-04 1.22E-04 6.82E-05 4.51E-05 resistance Viscous 100 54 30 20
resistance ratio (%) Pressure Ceiling 3358 2907 2010 743 chamber
portion area (.mu.m.sup.2) Ceiling 100 87 60 22 portion area ratio
(%)
[0007] The inertance and viscous resistance of the nozzle portion
101 act as resistance at the time of discharging ink, and when
these are large, an ejection energy efficiency falls. The inertance
and viscous resistance are expressed by the following formulas,
respectively.
[0008] Inertance M (kPa/(.mu.m.sup.3/.mu.s.sup.2)) M = .rho.
.times. .intg. 0 OP .times. .times. d x / s .function. ( x )
##EQU1## where,
[0009] OP: thickness of nozzle portion
[0010] S(x): ink flow path sectional area in position of distance x
from lower edge of nozzle portion (.mu.m.sup.2)
[0011] .rho.: specific gravity of ink
[0012] Viscous resistance R (kPa/(.mu.m.sup.3/.mu.s)) R = .eta.
.times. .intg. 0 OP .times. D .function. ( x ) .times. .times. d x
/ S .function. ( x ) 2 ##EQU2## where,
[0013] D(x) is a shape factor of a nozzle, and when a nozzle is a
rectangular solid:
D(x)=12.0.times.(0.33+1.02.times.(a(x)/b(x)+b(x)/a(x))) when a
nozzle is a cylinder: D(x)=8.pi.
[0014] OP: thickness of nozzle portion
[0015] S(x): ink flow path sectional area in position of distance x
from lower edge of nozzle portion (.mu.m.sup.2)
[0016] .eta.: ink viscosity (Pas)
[0017] In addition, since the inertance and viscous resistance in
Table 1 are used for relative comparison, they are obtained by
simple calculation.
[0018] Specifically, inertance is calculated on condition of
specific gravity .rho.=1, and, viscous resistance is calculated on
conditions of coefficient of sectional form of nozzle=1 and
viscosity .eta.=1e-3 Pas. This is common to all the values of
inertances and viscous resistances described below. In order to
obtain strict inertance, it is necessary to use the specific
gravity of ink to be used, and in order to obtain the strict
viscous resistance, it is necessary to calculate using a
coefficient of sectional form D(x) adapted to the viscosity .eta.
of ink and a cross-sectional form of a nozzle to be used.
[0019] As shown in Table 1, it is understood on a straight nozzle
that its inertance and viscous resistance are large and it is
inefficient. On the other hand, on a tapered nozzle, both of
inertance and viscous resistance become small as a taper angle is
enlarged. Specifically, at 5.degree. of taper angle, inertance
becomes 72% and, viscous resistance becomes 54% to a straight
nozzle. In addition, at 12.degree. of taper angle, the inertance
becomes 51%, which is nearly a half, and the viscous resistance
becomes 30% to the straight nozzle. Furthermore, at 19.degree. of
taper angle, the inertance becomes 39%, and the viscous resistance
becomes 20%, which is 1/5, to the straight nozzle. Thus, it is
possible to raise an ejection energy efficiency sharply in a
tapered nozzle by enlarging a taper angle.
[0020] Nevertheless, in a tapered nozzle as shown in FIGS. 8A and
8B, a ceiling portion area of the pressure chamber 103 shown by
hatching in the figure becomes small as a taper angle becomes large
(as to specific numerical values, refer to Table 1). The ceiling
portion area of the pressure chamber 103 decreases to 87% of a
straight nozzle at 5.degree. of taper angle, decreases to 60% at
12.degree. of taper angle, and decreases sharply to 22% in
19.degree. of taper angle. Since the ceiling portion area of the
pressure chamber 103 acts as resistance to the approximately
horizontal motion of ink to the ceiling portion when a bubble
disappears, the motion loss of the bubble in bubble disappearing
process becomes large and an impulse force at the time of bubble
disappearing becomes weak as this resistance becomes large. In the
tapered nozzle with small flow resistance, since the kinetic energy
of ink in a horizontal direction in the pressure chamber 103 also
becomes large in addition to the kinetic energy of the ink in the
nozzle portion 101 at the time of bubble disappearing being large
essentially, the impulse force generated at the time of bubble
disappearing becomes very large. As a result, the impulse force
generated at the time of bubble disappearing, i.e., the impulse
force generated at the time of cavitation collapse, become large,
and there has been a problem of being easy to damage the heater
102.
SUMMARY OF THE INVENTION
[0021] The present invention aims at providing an ink jet recording
head which controls an impulse force generated at the time of
disappearing of a bubble with keeping an energy efficiency of ink
ejection high.
[0022] The ink jet recording head of the present invention is
characterized by comprising a discharge port from which ink is
discharged, a pressure chamber by which energy for ejection is
given to ink, and a nozzle portion which makes the pressure chamber
and discharge port communicate, the nozzle portion including a
major diameter portion with a larger sectional area than an area of
the discharge port, and a minor diameter portion, whose sectional
area is smaller than that of the major diameter portion, along an
ink ejection direction, the minor diameter portion being provided
in a position nearer to the pressure chamber than the major
diameter portion.
[0023] According to the present invention, it is possible to reduce
the flow resistance of the nozzle portion with avoiding the
decrease of the ceiling area of the pressure chamber. Therefore, it
is possible to control the impulse force generated inside the
pressure chamber at the time of bubble disappearing with keeping
the energy efficiency of ink ejection high.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIGS. 1A and 1B are sectional views showing an example of an
embodiment of an ink jet recording head of the present invention,
FIG. 1A shows a section parallel to an ink ejection direction, and
FIG. 1B is a diagram showing a section which is orthogonal to the
ink ejection direction;
[0025] FIGS. 2A, 2B, 2C, 2D, 2E, 2F, 2G, 2H and 2I are sectional
views showing the manufacturing process of the recording head in
FIGS. 1A and 1B;
[0026] FIG. 3 is a sectional view showing another example of an
embodiment of the ink jet recording head of the present invention,
and is a diagram of a section parallel to the ink ejection
direction;
[0027] FIG. 4 is a sectional view showing still another example of
an embodiment of the ink jet recording head of the present
invention, and is a diagram of a section parallel to the ink
ejection direction;
[0028] FIG. 5 is a sectional view showing a further example of an
embodiment of the ink jet recording head of the present invention,
and is a diagram of a section parallel to the ink ejection
direction;
[0029] FIGS. 6A, 6B, 6C, 6D, 6E, 6F and 6G are sectional views
showing the manufacturing process of the recording head in FIG.
5;
[0030] FIGS. 7A and 7B are sectional views showing an example of a
conventional ink jet recording head, FIG. 7A shows a section
parallel to an ink ejection direction, and FIG. 7B is a diagram
showing a section which is orthogonal to the ink ejection
direction; and
[0031] FIGS. 8A and 8B are sectional views showing another example
of an embodiment of the conventional ink jet recording head, FIG.
8A shows a section parallel to an ink ejection direction, and FIG.
8B is a diagram showing a section which is orthogonal to the ink
ejection direction.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiment 1
[0032] Hereafter, an example of an embodiment of the ink jet
recording head of the present invention will be explained with
referring to FIGS. 1A and 1B. FIGS. 1A and 1B are enlarged
sectional views of a nozzle portion of the recording head of this
embodiment, and FIG. 1A shows a section parallel to an ink ejection
direction, and FIG. 1B shows a section orthogonal to the ink
ejection direction, respectively.
[0033] One end of the nozzle portion 1 communicates with a pressure
chamber 3 in which a heater 2 is provided, and another end
communicates with a discharge port 5 from which ink is discharged.
Furthermore, an ink flow path 6 for supplying ink to the pressure
chamber 3 communicates with the pressure chamber 3. The ink flow
path 6 communicates with an ink supply opening not shown, and ink
is supplied through this ink supply opening. The ink supplied from
the ink supply opening is supplied to the pressure chamber 3
through the ink flow path 6. Usually, the pressure chamber 3 and
nozzle portion 1 are filled with the ink supplied as mentioned
above, and a meniscus 7 of the ink is formed in a discharge port 5.
When the heater 2 generates heat in this state, the ink is heated
by heat and a predetermined amount of ink (ink droplet) is
discharged from the discharge port 5 by the pressure of a bubble
generated in the ink.
[0034] A major diameter portion 8 with a larger sectional area than
that of the discharge port 5 is formed in the middle of the nozzle
portion 1 in the ink ejection direction, and a minor diameter
portion 9 whose sectional area is smaller than that of the major
diameter portion 8 is formed between the major diameter portion 8
and pressure chamber 3. Because of having the major diameter
portion 8, the flow resistance of the nozzle portion 1 is small
drastically in comparison with that of a conventional straight
nozzle. Here, Table 2 shows the inertance and viscous resistance of
the nozzle portion 1, and ceiling portion area of the pressure
chamber 3 in two structure A and B between which distance ht from
the discharge port 5 to the major diameter portion 8, height hb of
the major diameter portion 8, and height hs of the minor diameter
portion 9 differ. It is common in the structure A and B that
distance OH from the discharge port 5 to a top face of the heater 2
is 75 .mu.m and the height H of the ink flow path 6 is 20 .mu.m. In
the structure A, ht=10 .mu.m, hb=35 .mu.m, and hs=10 .mu.m hold,
and in the structure B, ht=5 .mu.m, hb=45 .mu.m, and hs=5 .mu.m
hold. TABLE-US-00002 TABLE 2 Structure of Straight Tapered nozzle
present invention nozzle Taper 5.degree. Taper 12.degree. Taper
19.degree. A B Nozzle Inertance 1.12E-01 8.04E-02 5.72E-02 4.37E-02
5.86E-02 4.33E-02 portion Inertance ratio (%) 100 72 51 39 52 39
Viscous resistance 2.28E-04 1.22E-04 6.82E-05 4.51E-05 9.21E-05
5.32E-05 Viscous resistance ratio (%) 100 54 30 20 40 23 Pressure
Ceiling portion area (.mu.m.sup.2) 3358 2907 2010 743 3358 3358
chamber Ceiling portion area ratio(%) 100 87 60 22 100 100
[0035] The inertance of the nozzle portion of the structure A is
52% of that of a straight nozzle which is almost equal to that of a
tapered nozzle with 12.degree. of taper angle, and the inertance of
the nozzle portion of the structure B is 39% of the straight
nozzle, which is almost equal to that of a tapered nozzle with
19.degree. of taper angle.
[0036] Tn addition, the viscous resistance of the structure A is
40% of the straight nozzle, which is near to that of the tapered
nozzle with 12.degree. of taper angle, and the viscous resistance
of the structure B is 23% of the straight nozzle, which is
dramatically near to that of the tapered nozzle with 19.degree. of
taper angle. Thus, it turns out that, according to the present
invention, the resistance of a nozzle portion is reduced sharply
and the ejection energy efficiency improves remarkably.
[0037] On the other hand, the ceiling portion area of the pressure
chamber in the structure A and B is maintained at the same area as
the straight nozzle in each of the structure A and B as shown in
Table 3. Hence, the motion loss of ink approximately parallel to
the ceiling of the pressure chamber at the time of bubble
disappearing is sharply reduced in comparison with the conventional
tapered nozzle. As a result, the impulse force generated at the
time of disappearing of a bubble becomes weaker, damage to the
heater is reduced, and heater lifetime is extended greatly.
TABLE-US-00003 TABLE 3 Tapered Structure nozzle of Pro- Ta- Ta- Ta-
present tru- Straight per per per invention sion nozzle 5.degree.
12.degree. 19.degree. A B Pres- Not Ceiling 3358 2907 2010 743 3358
3358 sure pres- portion cham- ent area ber (.mu.m.sup.2) Ceiling
100 87 60 22 100 100 portion area ratio (%) Pres- Ceiling 3433 3013
2159 938 ent portion area (.mu.m.sup.2) Ceiling 102 90 64 28
portion area ratio (%)
[0038] As described above, according to the present invention, it
is possible to control the impulse force generated at the time of
disappearing of a bubble, to suppress damage to a heater, and to
prolong the disconnection lifetime of the heater exponentially,
with keeping the energy efficiency of ink ejection high.
[0039] In addition, also in any of a conventional straight nozzle
and a tapered nozzle, a convex protrusion may be generated around a
bottom end portion of a discharge port depending on manufacturing
process. However, the size of this protrusion is about at most 1
.mu.m, and most effects which it has on a ceiling portion area of a
pressure chamber can be disregarded. Specifically, when a taper
angle is 5.degree., the ceiling portion area of the pressure
chamber of a tapered nozzle becomes to the extent of 90% to a
straight nozzle when there is a protrusion, although it is 87% when
there is no protrusion. In addition, when the taper angle is
12.degree., the ceiling portion area of the pressure chamber of the
tapered nozzle becomes to the extent of 64% to the straight nozzle
when there is a protrusion, although it is 60% when there is no
protrusion. Furthermore, when the taper angle is 19.degree., the
ceiling portion area of the pressure chamber of the tapered nozzle
becomes to the extent of 28% to the straight nozzle when there is a
protrusion, although it is 22% when there is no protrusion.
[0040] As mentioned above, it is possible to disregard most effects
which a convex protrusion of the order of 1-.mu.m generated around
a bottom end portion of the discharge port in manufacturing process
has on the ceiling portion area of a pressure chamber, i.e.,
effects which it has on the approximately horizontal motion of ink
to the ceiling portion.
[0041] Next, FIGS. 2A to 2I show the manufacturing process of the
recording head of this embodiment. First, a positive type die
material 21 is coated on a substrate 20 where a heater not shown is
formed (FIG. 2A). Then, the die material 21 is exposed and
developed, and a pattern equivalent to a desired ink flow path is
formed (FIG. 2B). Next, a negative type nozzle material 23 is
coated on the die material 21 (FIG. 2C), portions other than a
portion which serves as a minor diameter portion of a nozzle
portion finally are exposed and developed, and the nozzle material
23 in the portion equivalent to the minor diameter portion is
removed (FIG. 2D). Next, a die material 25 is coated again (FIG.
2E), portions other than a portion which finally serves as a major
diameter portion are exposed and developed, and the die materials
25 in other than the portion equivalent to the major diameter
portion are removed (FIG. 2F). Then, a nozzle material 26 is coated
again (FIG. 2G), portions other than a portion equivalent to a
discharge port are exposed and developed, and the discharge port 5
is formed (FIG. 2H). Finally, all the die material 23 is developed,
and the nozzle portion 1, pressure chamber 3, and ink flow path 6
are formed (FIG. 2I).
Embodiment 2
[0042] Hereafter, a second embodiment of the present invention will
be described with referring to FIG. 3. The basic constitution of
the recording head of this embodiment is the same as that of the
recording head of the first embodiment. Difference is that a taper
portion which tapers off gradually from a side of the major
diameter portion 8 toward the discharge port 5 is provided between
the discharge port 5 and major diameter portion 8. In the recording
head of this embodiment, since the flow resistance of ink which
passes a taper portion 30 becomes small by providing the taper
portion 30, the flow resistance of the entire nozzle portion 1 is
further reduced with keeping the distance ht from the discharge
port 5 to the major diameter portion 8, the height hb of the major
diameter portion 8, and the height hs of the minor diameter portion
9 the same as those in the first embodiment. As a result, it
becomes possible to increase ejection energy efficiency further in
comparison with that of the recording head in the first embodiment.
In addition, since the ceiling portion area of the pressure chamber
3 is kept the same as that of the recording head in the first
embodiment, the effects that an impulse force generated at the time
of disappearing of a bubble is controlled, damage to the heater 2
is suppressed, and the disconnection lifetime of the heater 2 is
prolonged exponentially are not spoiled.
Embodiment 3
[0043] Hereafter, a third embodiment of the present invention will
be described with referring to FIG. 4. The basic constitution of a
recording head of this embodiment is the same as that of the
recording head in the second embodiment. Difference is that a minor
diameter portion 9 is formed by providing taper in a wall surface
31 between the minor diameter portion 9 of the nozzle portion 1 and
the pressure chamber 3 so that the nozzle portion 1 may taper off
gradually toward the pressure chamber 3.
[0044] In the recording head of this embodiment, the flow
resistance of the nozzle portion 1 becomes further smaller by an
synergistic effect of the taper portion 30 between the major
diameter portion 8 and discharge port 5, and the taper (taper in a
direction reverse to that of the taper portion 30) of the minor
diameter portion 9. Therefore, it is possible to reduce further the
flow resistance of the entire nozzle portion 1 with keeping the
distance ht from the discharge port 5 to the major diameter portion
8, the height hb of the major diameter portion 8, and the height hs
of the minor diameter portion 9 the same as those in the second
embodiment. As a result, it becomes possible to increase ejection
energy efficiency further in comparison with that of the recording
head in the second embodiment. In addition, since the ceiling
portion area of the pressure chamber 3 is kept the same as that of
the recording head in the second embodiment, the effects that an
impulse force generated at the time of disappearing of a bubble is
controlled, damage to the heater 2 is suppressed, and the
disconnection lifetime of the heater 2 is prolonged exponentially
are not spoiled.
Embodiment 4
[0045] Hereafter, a fourth embodiment of the present invention will
be described with referring to FIG. 5. The recording head of this
embodiment is characterized by not only forming the major diameter
portion 8 by providing taper in a position nearer to a side of the
discharge port 5 than an arbitrary position P of the nozzle portion
1 in an ink ejection direction so that a sectional area may be
gradually enlarged toward the pressure chamber 3 from the discharge
port 5, but also forming the minor diameter portion 9 with
providing reverse taper in a position nearer to a side of the
pressure chamber 3 than the above-mentioned position P so that a
sectional area may reduce toward the pressure chamber 3 gradually.
The recording head of this embodiment also exerts the effects that
the impulse force generated at the time of disappearing of a bubble
is controlled with the flow resistance of the entire nozzle portion
1 being reduced, and the ejection energy efficiency increasing.
[0046] FIGS. 6A to 6G show the manufacturing process of the
recording head of this embodiment. First, the positive type die
material 21 is coated on the substrate 20 where a heater not shown
is formed (FIG. 6A). Then, the die material 21 is exposed and
developed, and a pattern equivalent to a desired ink flow path is
formed (FIG. 6B). Next, the negative type nozzle material 23 is
coated on the die material 21 (FIG. 6C). The steps so far are the
same as the manufacturing process of the recording head of the
first embodiment. Next, exposure and development are performed so
that the above-mentioned reverse taper may be formed in a portion
equivalent to a minor diameter portion by making a mask for forming
an exposure pattern offset from a surface of the nozzle material 23
by a predetermined amount when exposing portions other than the
portion which finally serves as the minor diameter portion (FIG.
6D). Here, the die material 25 is coated again (FIG. 6E), exposure
and development are performed with adjusting the distance between
the mask and the surface of the die material 25 so that the
above-mentioned taper (major diameter portion) may be formed, and
then, the discharge port 5 and nozzle portion 1 (the minor diameter
portion 9 and major diameter portion 8) are formed (FIG. 6F).
Finally, the entire die material 21 is removed, and the pressure
chamber 3, and ink flow path 6 are formed (FIG. 6G).
[0047] As described above, since the recording head of this
embodiment can be produced by the process simpler than that of the
recording head in the first, second and third embodiments,
manufacturing cost is reduces greatly.
[0048] This application claims priority from Japanese Patent
Application No. 2004-354072 filed on Dec. 7, 2004, which is hereby
incorporated by reference herein.
* * * * *